fix: user uploaded themes are now stored in the config directory. Missing directories will be created and added docs for theming

docs/theming.md

@@ -0,0 +1,38 @@
+# Theming tidal-hifi
+
+## Table of contents
+
+<!-- toc -->
+
+- [Theming tidal-hifi](#theming-tidal-hifi)
+  - [Table of contents](#table-of-contents)
+  - [Custom CSS](#custom-css)
+  - [config](#config)
+  - [Warning! Themes might break](#warning-themes-might-break)
+
+<!-- tocstop -->
+
+By default tidal-hifi comes with a few themes.
+You can select these in the settings window under the theming tab as shown below.
+
+![Settings window with the theming tab opened](./images/theming.png)
+
+## Custom CSS
+
+The custom CSS will be added to the HTML document last.
+This means that it will overwrite any existing CSS, even that of themes, unless the original has an access modifier such as `$important`.
+
+![settings window on the theming tab with a custom CSS override](./images/customcss.png)
+
+## config
+
+The theme selector and customCSS are stored in the config file.
+The custom CSS is stored as a list of lines.
+
+![settings window on the theming tab next to the config file](./images/customcss-config.png)
+
+## Warning! Themes might break
+
+Themes might break at any point. Tidal changes their webpage structure a ton (they probably generate classNames and don't provide roles/ids/attributes.)
+
+If one breaks you can create an Issue on GitHub or ask for assistance in the [Discord channel](https://discord.gg/yhNwf4v4He).